How to reach out to team maintains Solver add-in for Excel?

eryondon 

As far as I know (which doesn't necessarily mean it's still the case today, as Office is constantly evolving), Teams sees an Excel workbook as Excel for web.

Add-in programs aren't supported in Excel for the web, you won't be able to use the Solver add-in to run what-if analysis on your data to help you find optimal solutions.

If you have the Excel desktop application, you can use the Open in Excel button to open your workbook to use the Solver add-in.

More help on using Solver
Solver Help at www.solver.com.

Define and solve a problem by using Solver

Hope I was able to help you with this information/links.

NikolinoDE

I know I don't know anything (Socrates)